In the conventional art, the imaging device of a camera unit or the like incorporated in a digital camera or on onboard camera has been provided with an photoelectric conversion imaging element for converting incident light into an electric signal. Recent years have witnessed a proposal of an imaging element (linear log sensor) capable of switching between a linear conversion operation and logarithmic conversion operation for electric signal according to the incident light quantity (Patent Documents 1 and 2).
When compared to an imaging element (linear sensor) that performs only the linear conversion operation, such an imaging element is characterized by wider dynamic range, and the entire luminance information can be represented by an electric signals even when a subject having a wide range of luminance has been imaged.
When compared to an imaging element (log sensor) that performs only the logarithmic conversion operation, the aforementioned imaging element avoids the problem wherein an decrease in amount of the data to be outputted, according to the luminance value, even within a predetermined range of luminance, with the result that a sufficient contrast of the subject can be ensured.
The linear log sensor is preferably used for imaging as a sensor having a photoelectric conversion function by fully utilizing respective advantages of each of the linear conversion operation and logarithmic conversion operation of the linear log sensor with respect to a main subject of imaging. To be more specific, when there is a wide range of the luminance of the captured image, the logarithmic conversion region of the imaging element is preferably used. When a sufficient contrast of the subject is desired, the linear conversion operation of the imaging element is preferably used to obtain sufficient data of electric signals in a specific luminance range for conducting an image processing.
Patent Document 1: Unexamined Japanese Patent Application Publication No. 2002-223392
Patent Document 2: Unexamined Japanese Patent Application Publication No. 2004-088312